This invention relates to outboard motors, and more particularly to a drive unit for use with the watercraft, such as a pleasure boat, with the capability to shift gears between a forward position and a reverse position.
Conventional marine outboard drive units are supported on the transom of a boat and can be pivoted to move in a generally horizontal plane, left and right, within a 45-90 degree arc. The outboard motors include a transmission mechanism for transmitting rotational power of the crankshaft of an engine to a propeller through a drive shaft. As a general rule, smaller outboard motors can propel the boat in a forward direction, with only a forward-shift capability. The larger motors that allow reverse movement of the boat are typically large, expensive, and have complicated gear-switching mechanisms.
An additional problem experienced by motor craft when running in shallow or muddy waters, is that the water body has overgrowth of vegetation which catches on the propeller and makes forward movement extremely difficult. Another problem is the possibility of the propeller striking rocks or other hard underwater objects causing severe damage to the propeller unit.
Still another problem that is encountered when using a small outboard motor unit is that when it is mounted on a tall transom boat the skeg of the propeller is insufficiently submerged to provide an effective steering on the water.
A further problem experienced with outboard motor units is the buildup of pressure inside the gearbox and the stuffing box, which results from the rotation of the shaft and the gears. The buildup of hot air pressure causes the seals to leak and allows water to enter resulting in inevitable danger to bearings and the gear.